Pulses are edible leguminous seeds, such as peas, beans, lentils etc. which have long been recognized as an important and inexpensive component of the human diet, providing a rich, low-fat source of protein, complex carbohydrates and dietary fibre.
The production of pulses with a long shelf life has been the subject of much investigation in the food industry. Traditionally pulses have been prepared for storage by dehydration. Dried pulses are widely available to consumers, who may reconstitute the dried pulses as desired by rehydrating them in water. The lengthy time required to rehydrate pulses to a soft edible texture by soaking and boiling is a disadvantage for many consumers and for commercial food preparation facilities. Attempts have been made to reduce the rehydration time required, for example by mechanically perforating the husks of the pulses, or by the addition of enzymes or softeners during the drying process (U.S. Pat. No. 4,214,007 to Hase). However, such methods frequently result in pulses which have undergone extensive changes in their appearance, structure and taste and which have unfavorable organoleptic properties. U.S. Pat. No. 3,867,553 to Hitze et al. describes the use of pectolytic enzymes in efforts to improve the properties of rehydrated peas. Hungarian Patent No. 193673 to Kurnik describes a process for freeze drying beans and peas.
In efforts to reduce the preparation time of pulses, dried pulses may be processed through a pre-cooking step prior to drying. Pre-cooked dried pulses, particularly beans have shown a tendency to crack, burst and become floury or grainy (U.S. Pat. No. 3,510,313 to Steinkraus). Complex processes have been tried in efforts to prepare pre-cooked dried beans having improved organoleptic properties. U.S. Pat. No. 4,333,955 describes a process for preparing fast cooking dried beans by boiling and soaking the beans, subjecting them to enzymatic treatment, an acidic boiling step and drying in superheated steam.
The appearance, taste, speed of rehydration and the inclusion of additives remain problematic with dried pulses and it has proven difficult to obtain beans which may be instantly reconstituted to provide pulses which duplicate the texture, taste and mouth-feel of freshly cooked pulses. Alternative methods for storing pulses include canning or freezing. Canned pulses are prepared at high temperature and have reduced food value and a soft mushy texture.
Generally frozen pulses, such as peas are prepared by blanching and freezing. Such pulses still require significant cooking before they are ready to eat. A process for preparing frozen, cooked, table-ready rehydrated legumes is described in U.S. Pat. No. 4,900,578 to Bakker. The process involves the steps of soaking, cooking and freezing the beans. However, such process steps tend to result in beans of poor appearance, which have wrinkled or fractured skins and which become agglomerated together on freezing. It has also proven difficult to use this process for preparing individually frozen pulses using commercial production line equipment, as the cooked pulses stick to the production line equipment, freezing units and belts and to each other. Attempts to scrape the freezing pulses off the belts results in significant damage to the integrity of the beans.
There is a need for a process for preparing individually frozen cooked pulses which may be instantaneously and conveniently restored to the soft edible appearance and condition of boiled pulses. In particular, there is a need for such a process by which pulses may be individually frozen on a commercial moving belt production line.